lavf/webm_chunk: Remove AVFMT_ALLOW_FLUSH

The flag was set unintentionally and the code will break if a NULL
packet is passed in.
Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/webm_chunk.c

@@ -256,7 +256,7 @@ AVOutputFormat ff_webm_chunk_muxer = {
     .mime_type      = "video/webm",
     .extensions     = "chk",
     .flags          = AVFMT_NOFILE | AVFMT_GLOBALHEADER | AVFMT_NEEDNUMBER |
-                      AVFMT_TS_NONSTRICT | AVFMT_ALLOW_FLUSH,
+                      AVFMT_TS_NONSTRICT,
     .priv_data_size = sizeof(WebMChunkContext),
     .write_header   = webm_chunk_write_header,
     .write_packet   = webm_chunk_write_packet,